Getting value from a custom user control in asp.net

Question

I'll probably answer my own question before I finish this post, but in case I fail here what I'm grappling with.

I need to get the PhotoId value out of Club:ImageThumbnail control:

<asp:FormView ID="fvPhpto" runat="server" DataKeyNames="id"
     Width="480px" AllowPaging="True"
     PagerSettings-Visible="false">
     <ItemTemplate>
       <asp:Label Text='<%# Eval("title") %>' runat="server" ID="descriptionLabel" />
       <Club:ImageThumbnail ID="thumb1" runat="server" ImageSize="Large" PhotoID='<%# Eval("id") %>' />
     </ItemTemplate>
     ...

This sort of thing int id = (int)fvPhpto.FindControl("thumb1").PhotoID; does not work as PhotoID won't show up in intellisence.

This is what the code in Club:ImageThumbnail looks like:

public object PhotoID
{
    get
    {
        object o = ViewState["PhotoID"];
        return (o != null) ? (int)o : 0;
    }
    set
    {
        ViewState["PhotoID"] = (value != null && value !=DBNull.Value) ? Convert.ToInt32(value) : 0;     
    }
}

public ImageSizes ImageSize
{
    get
    {
        object o = ViewState["ImageSize"];
        return (o != null) ? (ImageSizes)o : ImageSizes.Thumb;
    }
    set
    {
        ViewState["ImageSize"] = value;
    }
}

public enum ImageSizes
{
    Large = 0,
    Thumb = 1,
    FullSize = 2
}

public string NoPhotoImg
{
    get
    {
        object o = ViewState["NoPhotoImg"];
        return (o != null) ? (string)o : null;
    }
    set
    {
        ViewState["NoPhotoImg"] = value;
    }
}

protected void Page_PreRender(object sender, System.EventArgs e)
{
    if (Convert.ToInt32(PhotoID) == 0)
    {
        if (NoPhotoImg != null)
        {
            Image1.ImageUrl = NoPhotoImg;
        }
        else
        {
            Image1.Visible = false;
        }
    }
    else
    {
        Image1.ImageUrl = "ImageFetch.ashx?Size=" + Convert.ToInt32(ImageSize) + "&ImageID=" + Convert.ToString(PhotoID);
    }
}


<asp:Image ID="Image1" runat="server" CssClass="photo" BorderWidth="1" />

Karl Anderson · Accepted Answer · 2013-11-25 20:28:28Z

1

You need to cast to the user control type first and then to int for the photo ID value, like this:

int id = (int)(fvPhpto.FindControl("thumb1") as ImageThumbnail).PhotoID;

It is probably easier and clearer to understand if you split apart the casts into two steps, first to the user control type and then cast to the int, like this:

ImageThumbnail theUserControl = fvPhpto.FindControl("thumb1") as ImageThumbnail;

// Since the C# as operator returns null for a failed cast, then we need to 
// check that we actually have an object before we try to use it
if(theUserControl != null)
{
    int id = (int)theUserControl.PhotoID;
}

Note: If ImageThumbnail is not the name of your user control's class, then change ImageThumbnail to the name of your user control's class name.

edited Nov 25, 2013 at 20:28

answered Nov 25, 2013 at 20:23

Karl Anderson

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